Technical Field
Preferred embodiments relate to a control apparatus for an internal combustion engine, and more particularly to a control apparatus for an internal combustion engine that is suitable as an apparatus for controlling an internal combustion engine that includes an in-cylinder pressure sensor.
Background Art
In Japanese Patent Laid-Open No. 2008-069713, a combustion control apparatus for an internal combustion engine that includes an in-cylinder pressure sensor is disclosed. In the combustion control apparatus, data for mass fraction burned that is synchronized with a crank angle is calculated using an in-cylinder pressure sensor and a crank angle sensor, and an actual combustion start point and a combustion center are calculated based on the data. In addition, if a difference obtained by subtracting the actual combustion start point from the combustion center exceeds an upper limit, the combustion control apparatus determines that combustion has deteriorated, and implements a countermeasure for improving combustion, such as increasing the fuel injection amount. Note that, in Japanese Patent Laid-Open No. 2008-069713, as one example, an appropriate value during a period in which mass fraction burned is from 10 to 30 percent is used as the aforementioned actual combustion start point that is a crank angle at a time that combustion is actually started in a cylinder, and, for example, an appropriate value during a period in which mass fraction burned is from 40 to 60 percent is used as the combustion center.
In Japanese Patent Laid-Open No. 2011-106334, a method for estimating a heat release rate in a cylinder using a Wiebe function is disclosed. According to this estimation method, the average in-cylinder pressure and average in-cylinder temperature in a specific period as well as the volumetric efficiency of intake air, the engine speed, the fuel injection amount, the fuel injection pressure and the EGR rate are used as operating condition parameters to estimate the heat release rate.